The day after Facebook dropped 18% removing close to $120 billion from its valuation, Wall Street turned to Twitter. The latter's shares declined over 18% on Friday afternoon, and once again the culprit was future earnings expectations. After the market closed on Thursday, the company reported second quarter earnings of 17 cents a share, matching Wall Street estimates. Revenue, at $711 million, beat by $15 million the number expected by analysts. Still, it was not enough to stave off disaster.